There is currently a retail price advantage to using propane or natural gas as a fuel in motorized vehicles. Indeed, vehicles which are manufactured to operate on a primary fuel such as gasoline may be converted to operate on one of two or more alternative sources of fuel such as natural gas or propane.
Gaseous fuels such as propane and natural gas are generally stored in pressurized cylinders in which the gas is a manageable volume. Propane is a fuel which is in the gaseous state when at atmospheric pressure and room temperature (NPT). Where conditions of use are cold enough, propane pressure (partial pressure) will drop, with the result that most of any propane in a container will be in the liquid state. As a result propane pressure above the liquid/gas interface will be very low. This is problematic particularly when propane is used as a fuel source for a motorized vehicle used in locations where cold winter temperatures occur. Furthermore, as a container of propane, or other such fuel, is consumed the partial pressure of the gas drops which leads to difficulties in providing a constant pressure for the delivery of fuel to a fuel consuming device such as an automobile engine.
Previous low pressure gas vaporizers suffer from many disadvantages in that they are either too large; too inefficient, or too expensive to manufacture. Furthermore, they do not deliver propane gas at a substantially constant pressure, nor are they self-adjusting with temperature; and they cannot be used to start an engine at cold temperatures of, for example, less than 15.degree. C. As well, they are not sufficiently reliable over a wide temperature range to be used in motor vehicles; they do not permit a sufficiently quick start to be used in motor vehicles; nor are they sufficiently safe to be used in motor vehicles. Consequently there is a need for a combination shut-off valve, vaporizer and pressure regulator which is self-adjusting for optimal fuel delivery regardless of ambient temperature.